Patients will be hospitalized on a 200 mEg Na 1.0-1.2 Gm protein for 1-2 days. Baseline blood work will be done. On the morning of the test PAH and Insulin studies will be started. After the patient reaches steady state, the study drug will be administered. This is a double-blind crossover study using gadopentetate dimeglumine one week and placebo the other week. The patient will have two hospitalizations approximately one week apart.